During most surgical procedures, bodily fluids are directed and transferred to various locations with the assistance of artificial pumping apparatus. Major operations such as heart surgery have been accomplished by procedures that require general anesthesia, full cardiopulmonary bypass (CPB), and complete cessation of cardiopulmonary activity. For example, during open heart surgery, circulation must be maintained while delicate work is performed on fragile blood vessels.
As with most major operations, open heart surgery typically requires weeks of hospitalization and months of recuperation time for the patient. The average mortality rate with this type of procedure is low, but associated with a complication rate that is often much higher. While very effective in many cases, the use of open heart surgery to perform various surgical procedures such as coronary artery bypass grafting (CABG) is highly traumatic to the patient. These procedures require immediate postoperative care in an intensive care unit, a period of hospitalization for at least several days, and an extended recovery period. In addition, open heart procedures require the use of CPB which continues to represent a major assault on a host of body systems. For example, there is noticeable degradation of mental faculties following such surgeries in a significant percentage of CABG patients in the United States. This degradation is commonly attributed to cerebral arterial blockage from debris and emboli generated during the surgical procedure. At the same time, the dramatic increase in the life expectancy of the general population has resulted in patients that are more likely to be older and sicker, with less cardiovascular, systemic, and neurologic reserve. As a consequence, inflammatory, hemostatic, endocrinologic, and neurologic stresses are tolerated much less by a significant number of patients today, and play a more significant role in CPB-induced morbidity.
The CABG procedure generally involves open chest surgical techniques to treat diseased vessels. During this procedure, the sternum of the patient is cut in order to spread the chest apart and provide access to the heart. The heart is stopped, and blood is thereafter cooled while being diverted from the lungs to an artificial oxygenator. In general, a source of arterial blood is then connected to a coronary artery downstream from the occlusion. The source of blood is often an internal artery, and the target coronary artery is typically among the anterior or posterior arteries which may be narrowed or occluded.
The combined statistics of postoperative morbidity and mortality continue to illustrate the shortcomings of CPB. The extracorporeal shunting and artificially induced oxygenation of blood activates a system wide roster of plasma proteins and blood components in the body including those that were designed to act locally in response to infection or injury. When these potent actors are disseminated throughout the body without normal regulatory controls, the entire body becomes a virtual battleground. The adverse hemostatic consequences of CPB also include prolonged and potentially excessive bleeding. CPB-induced platelet activation, adhesion, and aggregation also contribute to a depletion in platelet number, and is further compounded by the reversibly depressed functioning of platelets remaining in circulation. The coagulation and fibrinolytic systems both contribute to hemostatic disturbances during and following CPB. However, the leading cause of morbidity and disability following cardiac surgery is cerebral complications. Gaseous and solid micro and macro emboli, and less often perioperative cerebral hypoperfusion, produce neurologic effects ranging from subtle neuropsychologic deficits to fatal stroke. Advances in computed tomography, magnetic resonance imaging, ultrasound, and other imaging and diagnostic techniques have added to the understanding of these complications. But with the possible exception of perioperative electroencephalography, these technologies do not yet permit real time surgical adjustments that are capable of stopping a stroke in the making. Doppler and ultrasound evaluation of the carotid artery and ascending aorta, and other diagnostic measures, can also help identify surgical patients at elevated risk for stroke which are among the growing list of pharmacologic and procedural measures for reducing that risk.
CPB also affects various endocrine systems, including the thyroid gland, adrenal medulla and cortex, pituitary gland, pancreas, and parathyroid gland. These systems are markedly affected not only by inflammatory processes, but also by physical and biochemical stresses imposed by extracorporeal perfusion. Most notably, CPB is now clearly understood to induce euthyroid-sick syndrome which is marked by profoundly depressed triiodothyronine levels persisting for days following cardiothoracic surgery. The efficacy of hormone replacement regimens to counteract this effect are currently undergoing clinical investigation. By contrast, levels of the stress hormones epinephrine, norepinephrine, and cortisol are markedly elevated during and following CPB, and hyperglycemia is also possible.
Alternatives to CPB are limited to a few commercially available devices that may further require major surgery for their placement and operation such as a sternotomy or multiple anastomoses to vessels or heart chambers. For example, some present day devices used in CPB may require a sternotomy and an anastomosis to the ascending aorta for placement. The main drawbacks of these devices include their limited circulatory capacity which may not totally support patient demands, and their limited application for only certain regions of the heart such as a left ventricular assist device. These types of devices typically require direct access to the heart region and open heart surgery. Other available devices that permit percutaneous access to the heart similarly have disadvantages such as their limited circulatory capabilities due to the strict size constraints for their positioning even within major blood vessels. Moreover, the relative miniaturization of these types of devices present a high likelihood of mechanical failure. In further attempts to reduce the physical dimensions for cardiac circulatory apparatus, or any other bodily fluid transport system, the flow capacity of these devices are significantly diminished.
It would therefore be desirable to provide other less traumatic and more efficacious methods and techniques for controlling fluids while performing heart surgery or any other type of major operation. It would be particularly desirable if such techniques did not require the use of CPB or a sternotomy. It would be even more desirable if such apparatus and techniques could be performed using thoracoscopic methods that have been observed to decrease morbidity and mortality, cost, and recovery time when compared to conventional open surgical procedures.
Another significant disadvantage of surgical procedures on the heart and other fluid transport systems within the body is their inherent structural instability. The relative flexibility and wide range of movement of organ walls, cavities or the like often complicates delicate procedures that demand a stable operating platform. For example, the instability of unsupported cardiac walls, particularly when the heart is still beating, present significant challenges to the surgeon in performing CABG or other similar procedures. A variety of tools or probes are currently used in an attempt to minimize the movement of a tissue wall, organ or cavity wall, such as the exterior heart wall, and is a well recognized method used during CABG surgery on a beating heart. For example, a probe may be used that consists of a forked pedal placed directly onto the surface of a beating heart. These devices and other similar implements simply compress the outside wall of the heart or any other relatively unstable body surface to reduce its movement, and allows a surgeon to operate in a slightly more controlled environment. Other commonly used tools that provide similar functions may consist of a series of suction cups that uses suction force to suspend or hold areas surrounding the external surface of a surgical site in order to reduce undesirable movement. These and other known devices generally hold or immobilize only the external surface of an organ or unsupported wall to reduce movement at the surgical site.
During cardiac surgery, the heart is either still beating or immobilized entirely which requires further use of CPB. In the past, bypass surgery on a beating heart was limited to only a small percentage of patients requiring the surgical bypass of an occluded heart vessel. These patients typically could not be placed on CPB to arrest the heart, and were operated on while the heart kept beating. Meanwhile, patients whose hearts were immobilized and placed on CPB often suffered major side effects as previously described.
The medical community is currently performing more beating heart bypass surgery in an effort to avoid the use of artificial heart-lung machines. The need for apparatus and equipment to minimize the heart movement during surgery is ever increasing but very limited to a small number of devices designed for this specific application. Many devices in use today affect the heart motion by only interacting with its external wall while the inside wall of the heart is free to move about which does not create a motionless surgical site. In bypass surgery, it is particularly desirable to maintain the operating site relatively motionless during the suturing of these small vessels. Any compromise in the quality and integrity of the sutured vessel results in immediate or delayed complication that may be life threatening or require additional surgery. It is therefore desirable to perform beating heart surgery at surgical sites that remain relatively motionless. In order to achieve relative stability with beating heart surgery, it is desirable for the operation site be held relatively motionless by stabilizing both the outside and inside surfaces of the organ, or fixing the external and internal surfaces of a body wall. The stabilization mechanism should also not interfere significantly with the internal flow of fluids such as blood, or interfere with blood circulation by affecting heart rhythm through the application of any significant force to the heart wall, particularly when a patient has a low threshold for manipulating the external wall of the heart. Any significant manipulation of the heart itself may lead to heart fibrillation or arrhythmia, and presents an increased risk to the health of the patient.